Micro-transfer printing stamps and components

ABSTRACT

A micro-transfer structure comprises a stamp comprising a rigid support, only a single contiguous bulk layer disposed on the rigid support, and posts disposed on the bulk layer. Components are adhered to (e.g., disposed in contact with) some but not all of the posts. The posts can be substantially identical and disposed in a regular array on the bulk layer. Each component is adhered to (e.g., in contact with) two or more posts. Components can be disposed on a source wafer entirely over sacrificial portions of a sacrificial layer on or in the source wafer and attached to anchors disposed between sacrificial portions with a tether.

TECHNICAL FIELD

The present disclosure generally relates to micro-transfer printingstamps and micro-transfer printable components.

BACKGROUND

Substrates with electronically active components distributed over theextent of the substrate are used in a variety of electronic systems, forexample, in flat-panel display components such as flat-panel liquidcrystal or organic light emitting diode (OLED) displays, in imagingsensors, and in flat-panel solar cells. The electronically activecomponents are typically either assembled on the substrate, for exampleusing individually packaged surface-mount integrated-circuit componentsand pick-and-place tools, or by coating a layer of semiconductormaterial on the substrate and then photolithographically processing thesemiconductor material to form thin-film circuits on the substrate.Individually packaged integrated-circuit components typically havesmaller transistors with higher performance than thin-film circuits butthe packages are larger than can be desired for highly integratedsystems.

Methods for transferring small, active components from one substrate toanother are described in U.S. Pat. Nos. 7,943,491, 8,039,847, and7,622,367. In some such approaches, small integrated circuits are formedon a native semiconductor source wafer. The small, unpackaged integratedcircuits, or chiplets, are released from the native source wafer bypattern-wise etching portions of a sacrificial layer located beneath thechiplets, leaving each chiplet suspended over an etched sacrificiallayer portion by a tether physically connecting the chiplet to an anchorseparating the etched sacrificial layer portions. A viscoelastic stampis pressed against the process side of the chiplets on the native sourcewafer, adhering each chiplet to an individual stamp post. The stamp withthe adhered chiplets is removed from the native source wafer. Thechiplets on the stamp posts are then pressed against a non-native targetsubstrate or backplane with the stamp and adhered to the targetsubstrate.

In another example, U.S. Pat. No. 8,722,458 entitled Optical SystemsFabricated by Printing-Based Assembly teaches transferringlight-emitting, light-sensing, or light-collecting semiconductorelements from a wafer substrate to a destination substrate or backplane.Such micro-transferred components provide the high performance ofcrystalline semiconductor components together with the small size ofunpackaged dies.

Micro-transfer printing stamps are an important part of anymicro-transfer printing system and method. There is an ongoing need,therefore, for stamp structures that are highly reliable and easy-to-usefor a variety of component micro-transfer printing processes.

SUMMARY

The present disclosure provides, inter alia, structures and methods formore efficiently micro-transfer printing components from a source waferto a target substrate. According to some embodiments of the presentdisclosure, a micro-transfer structure comprises a stamp comprising arigid support, a bulk layer disposed on the rigid support, and postsdisposed on the bulk layer. The bulk layer can be, for example, only asingle contiguous bulk layer and, for example, having a contiguousplanar surface opposite the rigid support. Components are adhered to(e.g., disposed in contact with) some but not all of the posts. Theposts can be, but are not necessarily, substantially identical and canbe, but are not necessarily, disposed in a regular array on the bulklayer. Each component is adhered to (e.g., in contact with) two or moreposts. Each post can have (i) a substantially planar distal end, (ii) acontiguous distal end, or (iii) both (i) and (ii). In some embodiments,at least some posts are not in contact with any component. The bulklayer, the posts, or both the bulk layer and the posts can beelastomeric (e.g., comprise or consist essentially ofpolydimethylsiloxane).

According to some embodiments of the present disclosure, amicro-transfer structure comprises a stamp comprising a rigid supportand posts disposed on or over the rigid support and components adheredto (e.g., disposed in contact with) some but not all of the posts. Eachcomponent is adhered to (e.g., in contact with) two or more posts and atleast some posts are not adhered to (e.g., in contact with) a component.A single contiguous bulk layer can be disposed on the rigid support andthe posts can be disposed on the bulk layer. The bulk layer can be moreflexible than the rigid support and as flexible as, or less flexiblethan, the posts.

According to some embodiments, the bulk layer comprises a common layerdisposed on the rigid support and one or more pedestals disposed on thecommon layer on a side of the common layer opposite the rigid support,wherein two or more posts are disposed on each pedestal of the one ormore pedestals. The pedestal can be at least as flexible as, or moreflexible than, the common layer and the posts can be as flexible as ormore flexible than the pedestal, the common layer, or the bulk layer,and more flexible than the rigid layer.

According to some embodiments of the present disclosure, amicro-transfer structure comprises a component source substrate and thecomponents are disposed on the component source substrate. According tosome embodiments of the present disclosure, a micro-transfer structurecomprises a motion platform and the component source substrate is incontact with, and the component source substrate's position controlledby, the motion platform. According to some embodiments of the presentdisclosure, a micro-transfer structure comprises a target substrate andthe components are disposed on the target substrate. According to someembodiments of the present disclosure, a micro-transfer structurecomprises a motion platform and the target substrate is in contact with,and the target substrate's position controlled by, the motion platform.According to some embodiments of the present disclosure, amicro-transfer structure comprises a motion platform and the rigidsupport of the stamp is in contact with, and the rigid support'sposition controlled by, the motion platform.

According to some embodiments, each component is adhered to (e.g., incontact with at least two, four, six, ten, twelve, or fifteen posts. Theposts can be arranged in rows and columns, each component can have anedge or side, and the edge or side can be aligned with a row or columnor with both a row and a column.

According to some embodiments of the present disclosure, the stamp is afirst stamp, the rigid support is a first rigid support, the posts arefirst posts, each of the components has a first side opposite a secondside, and the first posts of the first stamp are adhered to (e.g., incontact with)) the first side of the component. Micro-transferstructures of the present disclosure can comprise a second stamp, thesecond stamp comprising a second rigid support different from the firstrigid support, a bulk layer different from the first bulk layer disposedon the second rigid support, for example only a single second contiguouselastomeric bulk layer, and second posts different from the first postsdisposed on the second bulk layer. In some embodiments, each second postis adhered to (e.g., in contact with) the second rigid support and nosecond bulk layer is present. The second sides of the components can beadhered to the second posts of the second stamp. Each component can bedisposed in contact with and adhered to fewer second posts on the secondside of the component than first posts of the first stamp on the firstside of the component. In some embodiments, (i) only one second post isadhered to each component, (ii) more than one second post is adhered toeach component, (iii) not all of the second posts are adhered to eachcomponent, (iv) both (i) and (iii), or (v) both (ii) and (iii).

Each first post can have a distal end with a first post area, eachsecond post of the second posts can have a distal end with a second postarea, and the second post area can be greater than the first post area.The sum of the first post areas in contact with each of the componentscan be smaller than the sum of the second post areas in contact witheach of the components. The second posts can be more adhesive than thefirst posts. Each post can have a distal end with a post area, eachcomponent can have a component area, for example on a process side ofthe component, and the post area can be less than one half of thecomponent area.

Micro-transfer structures of the present disclosure can comprise amotion platform and the first rigid support can be in contact with andcontrolled by the motion platform and the second rigid support can be incontact with and controlled by the motion platform.

Methods of the present disclosure can comprise providing a source waferwith components disposed in, on, or over the source wafer, providing astamp comprising a rigid support and posts disposed on or over the rigidsubstrate. Methods can comprise disposing the posts in contact with thecomponents so that two or more of the posts are in contact with eachcomponent to adhere the components to the posts and removing the stampwith the components from the source substrate. In some embodiments, atleast one post is not in contact with a component.

Methods of the present disclosure can comprise providing a source waferwith components disposed in, on, or over the source wafer, providing astamp comprising a rigid support, only a single bulk layer disposed onthe rigid support, and posts disposed on the bulk layer. Methods cancomprise disposing the posts in contact with the components so that twoor more of the posts are in contact with each component to adhere thecomponents to the posts and removing the stamp with the components fromthe source substrate.

According to some embodiments, the stamp is a first stamp, the rigidsupport is a first rigid support, the posts are first posts, each of thecomponents has a first side opposite a second side, and the first postsare in contact with the first side. Methods can comprise providing asecond stamp, the second stamp comprising a second rigid supportdifferent from the first rigid support, only a single second bulk layerdifferent from the first bulk layer disposed on the second rigidsupport, and second posts different from the first posts disposed on thesecond bulk layer. In some embodiments, each second post is adhered to(e.g., in contact with) the second rigid support and no second bulklayer is present. The second posts can be adhered to (e.g., disposed incontact with) the second side of the components with fewer of the secondposts in contact with the second side of each component than first postson the first side, thereby adhering the components to the second stampwhile the components are adhered to the first stamp. Methods can furthercomprise removing the first stamp, contacting the components to thetarget substrate with the second stamp, and removing the second stamp.

Structures and methods described herein enable a release and printingprocess for micro-transfer printing components from a source wafer to atarget substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects, features, and advantages ofthe present disclosure will become more apparent and better understoodby referring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a micrograph of a micro-transfer structure according toillustrative embodiments of the present disclosure;

FIG. 2 is a micrograph of a micro-transfer printing stamp according toillustrative embodiments of the present disclosure;

FIG. 3 is a cross section of a stamp according to illustrativeembodiments of the present disclosure;

FIG. 4 is a cross section of printable components on a component sourcewafer according to illustrative embodiments of the present disclosure;

FIG. 5 is a cross section of a second stamp according to illustrativeembodiments of the present disclosure;

FIG. 6 is a cross section illustrating a first stamp in contact withprintable components on a component source wafer according toillustrative embodiments of the present disclosure;

FIG. 7 is a cross section illustrating a first stamp with printablecomponents removed from a component source wafer according toillustrative embodiments of the present disclosure;

FIG. 8 is a cross section illustrating a stamp-to-stamp transfer ofcomponents from a first stamp to a second stamp according toillustrative embodiments of the present disclosure;

FIG. 9 is a cross section illustrating components adhered to a secondstamp according to illustrative embodiments of the present disclosure;

FIG. 10 is a cross section illustrating a second stamp printing adheredcomponents to a target substrate according to illustrative embodimentsof the present disclosure;

FIG. 11 is a cross section illustrating components printed to a targetsubstrate according to illustrative embodiments of the presentdisclosure;

FIG. 12A is a cross section illustrating a second stamp according toillustrative embodiments of the present disclosure;

FIG. 12B is a cross section illustrating a stamp-to-stamp transfer ofcomponents from a first stamp to the second stamp of FIG. 12A accordingto illustrative embodiments of the present disclosure;

FIG. 12C is a cross section illustrating micro-transfer printingcomponents adhered to the second stamp of FIG. 12A to a target substrateaccording to illustrative embodiments of the present disclosure;

FIG. 12D is a cross section illustrating directly micro-transferprinting components adhered to the first stamp of FIG. 3 to a targetsubstrate according to illustrative embodiments of the presentdisclosure;

FIG. 12E is a cross section illustrating micro-transfer printingcomponents with a first stamp from a handle substrate in flippedconfiguration according to illustrative embodiments of the presentdisclosure;

FIG. 13 is a cross section illustrating a first stamp with pedestalsaccording to illustrative embodiments of the present disclosure;

FIG. 14 is a cross section illustrating a second stamp with pedestalsaccording to illustrative embodiments of the present disclosure;

FIG. 15 is a cross section of a stamp according to illustrativeembodiments of the present disclosure; and

FIG. 16 is a flow diagram according to illustrative methods of thepresent disclosure.

Features and advantages of the present disclosure will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The figures are not drawn to scalesince the variation in size of various elements in the Figures is toogreat to permit depiction to scale.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The present disclosure provides, inter alia, a structure and method formicro-transfer printing components from a component source substrate toa target substrate, for example that are in an inverted or flippedconfiguration. U.S. Pat. No. 8,889,485 entitled Methods for SurfaceAttachment of Flipped Active Components by Bower describes a process formicro-transfer printing components (for example devices such assemiconductor integrated circuits) in a flipped configuration, as shownin the FIG. 8 flow diagram of the disclosure. As graphically illustratedin FIGS. 3A-3C of the Bower disclosure, components are transferred froma first stamp to a second stamp. In this method, each component iscontacted by a single stamp post for both the first and second stamps.The posts of the second stamp have a greater area in contact with thecomponents than the posts of the first stamp (FIGS. 3A, 3B, col. 10lines 20-30).

According to some embodiments of the present disclosure and as shown inthe micrograph of FIG. 1 , a micro-transfer structure 99 comprises astamp 30 comprising a bulk layer 34 and posts 36 disposed on bulk layer34. Components 20 are disposed in contact with and adhered to some butnot all of posts 36. Posts 36 can be substantially identical. Posts 36can be disposed in a regular array on bulk layer 34. Each component canbe in contact with two or more posts 36. For example, as shown in FIG. 1, each component 20 can be in contact with at least four, six, eight,ten, twelve, fifteen, or more posts 36. Posts 36 of stamp 30 can beregularly arranged, for example in rows of posts 36 spaced apart by asame distance, in columns of posts 36 spaced apart by a same distance,or in both rows and columns of posts 36 spaced apart by a same distance.In some embodiments, each component 20 has a component edge or componentside 28, and component edge or component side 28 is aligned (e.g.,parallel) with a row or column of posts 36 or a first component edge orcomponent side 28 is aligned with a row of posts 36 and a secondcomponent edge or component side 28 is aligned with a column of posts36. As shown in FIG. 1 , most of components 20 are aligned with rows andcolumns of posts 36, but some components 20 are not. According to someembodiments, each post 36 has a distal end with a post area, eachcomponent 20 has a component area, and the post area of an individualpost 36 in contact with component 20 is less than 50% of the componentarea, for example less than or equal to 25%. 10%, 5%, or 1% of thecomponent area.

Referring to the micrograph of FIG. 2 and the illustration of FIG. 3 ,stamp 30 comprises a rigid support 32, only a single, contiguous bulklayer 34 disposed on rigid support 32 (e.g., without any additional mesaor pedestal), and all of posts 36 are disposed on bulk layer 34. In theillustration of FIG. 15 , stamp 30 posts 36 are disposed directly onrigid support 32. Stamps 30 can be any visco-elastic material orelastomer, for example polydimethylsiloxane (PDMS), and can be made bycasting liquid material on or in a mold, cured, and the mold removed.The mold can be made using photolithographic methods and materials, forexample photolithographic processing of a wafer of silicon. A stamp post36 extends from bulk layer 34 or rigid substrate 32 to a post distal endhaving a post surface that, for at least some of posts 36, is in atleast partial contact with a component 20. The post distal end can besubstantially planar, can be contiguous, or can be both planar andcontiguous, as shown in FIGS. 1 and 2 . A planar post distal end is allin a single plane and a contiguous post distal end is in one connectedportion, for example having a perimeter that is a simple closed curve,and not, for example, comprising two separate islands. Bulk layer 34 cancomprise a same material as posts 36 and can be equally flexible (e.g.,have a common Young's modulus). In some embodiments, bulk layer 34comprises the same material(s) as posts 36 but in different proportions,so that posts 36 are more flexible than bulk layer 34. In someembodiments, bulk layer 34 comprises different materials than posts 36and posts 36 are more flexible than bulk layer 34 (e.g., have a lowerYoung's modulus). Rigid support 32 can be, for example, any suitablewafer or rigid structure with a substantially planar surface suitablefor processing, for example glass, silicon, sapphire, or quartz. Rigidsupport 32 is less flexible than bulk layer 34 and less flexible thanposts 36.

In some embodiments of the present disclosure and as illustrated in FIG.4 , component 20 can be disposed or formed on a substrate 10 (e.g., acomponent source wafer 10 or a native component source wafer 10) andcomponents 20 are disposed on substrate 10. Source wafer 10 can comprisea sacrificial layer 12 comprising sacrificial portions 14 laterallyseparated by anchors 16. Components 20 are physically connected toanchors 16 by tethers 18. Each of components 20 can have a first side 21opposite a second side 22. First side 21 can be on a side of component20 opposite source wafer 10 and second side 22 can be on an oppositeside of component 22 adjacent to source wafer 10. In embodiments,sacrificial portions 14 are sacrificed, for example by dry or wetetching, so that sacrificial material in sacrificial portions 14 isremoved to form a gap 15 (as shown in micro-transfer structure 99 ofFIG. 6 ). Component 20 can be encapsulated by encapsulation layer 24forming component structure 26 to protect components 20 fromenvironmental contaminants. Encapsulation layer 24 can also coatportions of sacrificial layer 12 or source wafer 10 and anchors 16. Insome embodiments, tether 18 comprises portions of encapsulation layer 24or a portion of encapsulation layer 24 forms tether 18, as shown in FIG.4 . Component structure 26 can comprise component 20, encapsulationlayer 24 on component 20, and tether 18 or a portion (e.g., fractured orseparated portion) of tether 18.

In some embodiments of the present disclosure, stamp 30 can be a firststamp, rigid support 32 is a first rigid support, and posts 36 are firstposts 36. Referring to FIG. 5 and according to some embodiments of thepresent disclosure, a second stamp 40 comprises a second rigid support32 different from first rigid support 32, only a single second bulklayer 34 different from first bulk layer 34 disposed on second rigidsupport 32 (e.g., with no additional pedestal or mesa layer), and secondposts 46 different from first posts 36 disposed on second bulk layer 34(or, in embodiments that do not comprise a second bulk layer 34, secondposts 46 are disposed directly on second rigid support 32). Second posts46 can be larger than and have a larger area on distal ends of secondposts 46 than an area of the distal ends of first posts 36, for examplean area in contact with components 20. Thus, each first post 36 has adistal end with a first post area, each second post 46 has a distal endwith a second post area, and the second post area can be greater thanthe first post area.

Second stamp 40 can remove components 20 from first stamp 30. As shownin FIG. 6 , each component 20 is disposed in contact with and adhered tofewer second posts 46 on second side 22 than first posts 36 on firstside 21. In some embodiments of the present disclosure, (i) only onesecond post 46 is adhered to each component 20 (e.g., as shown in FIG. 6), (ii) more than one second post 46 is adhered to each component 20,(iii) not all of second posts 46 are adhered to the components 20, (iv)both (i) and (iii), or (v) both (ii) and (iii). Thus, where more thanone second post 46 is adhered to each component 20 some of second posts46 are not necessarily adhered to any component 20, for example as withfirst posts 36 in FIGS. 1 and 6 , although second posts 46 are largerthan or have more area at distal ends of second posts 46 in contact witha component 20 than first posts 36 have in contact with component 20.

In some embodiments, all second posts 46 are in contact with a component20. According to some embodiments, the sum of the first post areas incontact with a component 20 is smaller than the sum of second post areasin contact with a component (even if only a single second post 46 is incontact with component 20). Thus, if first and second posts 36, 46adhere to a component 20 with an equal strength per contact area,components 20 will preferentially adhere to second stamp 40 becausesecond stamp has a greater total second post area in contact withcomponents 20 than the total first post contact area of first stamp 30and therefore a greater adhesion and, when first and second stamps 30,40 are removed from each other, components 20 will adhere to secondstamp 40 in preference to first stamp 30.

In some embodiments of the present disclosure, second posts 46 comprisedifferent materials or different mixtures of materials than first posts36, so that second posts 46 are more adhesive than first posts 36 andcomponents 20 can preferentially adhere with more strength to secondposts 46 than to first posts 36.

The positions and movements of first and second stamps 30, 40 andsubstrate 10 can be controlled by a motion platform 60 (e.g., a 2D or 3Dmotion platform 60). For example, first rigid support 32 of first stamp30 and second rigid support 32 of second stamp 40 can be in contactwith, and their movements controlled by, the motion platform 60. Amotion platform 60 can be a mechatronic system that uses an opticalcamera to align stamp 30 to components 20.

FIGS. 6-11 and flow diagram FIG. 16 sequentially illustrate the processof micro-transfer printing components 20, according to some embodimentsof the present disclosure. As shown in FIG. 6 , a source wafer 10 withcomponents 20 on substrate 10 is provided in step 100, a first stamp 30is provided in step 110, and first sides 21 of components 20 arecontacted with stamp posts 36 of first stamp 30 in step 120. As shown inFIG. 7 , in step 130 first stamp 30 is removed from substrate 10,fracturing or separating tethers 18 connecting components 20 to anchors16 of substrate 10 and adhering components 20 to stamp posts 36. In step140 and as shown in FIG. 8 , second stamp 40 is provided and, in step150, second posts 46 contact second sides 22 of components 20. Fewersecond posts 46 can contact components 20 than first posts 36, secondposts 46 can be larger or more adhesive than first posts 36, and agreater second post area can contact component 20 than a first postarea. As shown in FIG. 9 , in step 160 first stamp 30 is removed,leaving components 20 adhered to second stamp posts 46 of second stamp40.

A target substrate 50 is provided in step 170, as shown in FIG. 10 , anda motion platform 60 contacts first sides 21 of components 20 on secondposts 46 to target substrate 50 in step 180. Second stamp 40 is thenremoved in step 190, leaving components 20 adhered to target substrate50, as shown in FIG. 11 .

In some embodiments of the present disclosure and as shown in FIG. 12A,second stamp 40 provides multiple second posts 46 in contact withcomponents 20, but fewer second posts 46 in contact with components 20than first posts 36 of first stamp 30, as illustrated in FIG. 12B. Thesecond post area in contact with component 20 is larger than the firstpost area in contact with component 20, even though there are fewersecond posts 46 than first posts 36 in contact with component 20. FIG.12B illustrates a stamp-to-stamp transfer using first and second stamps30, 40 of FIG. 3 and FIG. 12A, respectively. FIG. 12C illustratesprinting from second stamp 40 of FIG. 12A to target substrate 50 so thatcomponents 20 are adhered to target substrate 50 in a flipped (inverted)configuration. In some embodiments, components 20 are printed directlyfrom first stamp 30 to target substrate 50. In some such embodiments,components 20 are not micro-transfer printed in a flipped configuration,as shown in FIG. 12D with first stamp 30.

According to some embodiments and as shown in FIGS. 13 and 14 , bulklayer 34 of first stamp 30 or of second stamp 40, or both, can comprisea common layer 38 and one or more pedestals 39. Common layer 38 isdisposed on rigid support 32 and pedestals 39 are disposed on commonlayer 38 on a side of common layer 38 opposite rigid support 32. Two ormore posts 36 are disposed on each pedestal 39 of the one or morepedestals 39. Pedestal 39 is at least as flexible as common layer 38. Insome embodiments, pedestal 39 is more flexible than common layer 38. Theuse of pedestals 39 on a common layer 38 can improve accuracy bydecreasing runout due to curing the stamp material at a temperaturegreater than the temperature at which stamps 30 are used.

Stamps 30 of the present disclosure provide an advantage in that theyoperate to pick up components 20 without requiring careful alignmentwith a component 20 source substrate 10, since posts 36 can contactcomponents 20 regardless of the relative orientation and position ofstamp 30 and substrate 10. Moreover, by employing a first stamp 30 withposts 36 with a relatively smaller surface area in contact withcomponents 20, components 20 can be transferred to a second stamp 40with fewer, larger second posts 46 with a relatively greater area incontact with components 20, enabling printing components 20 on a targetsubstrate 50 in a flipped configuration. Again, in some embodiments,relatively smaller posts 36 on a second stamp 40 can be used to transfercomponents 20 to second stamp 40 from first stamp 30 without requiringcareful alignment of first stamp 30 and second stamp 40. In someembodiments, substrate 10 (source wafer 10) can be provided as aflip-chip wafer with components 20 adhered to a handle substrate andstamps 30 of the present disclosure can micro-transfer print components20 from the handle substrate to a target substrate 50, either directlyin a flipped configuration, or indirectly with a second stamp 40 thatdisposes components 20 in a conventional, non-flipped configuration.Some such embodiments are useful when it is difficult to form asacrificial layer 12 in or on native source wafer 10 on which components20 are constructed. Components 20 can then be adhered to the handlewafer, native source wafer 10 removed, e.g., by grinding or laserlift-off, leaving components 20 adhered to the handle wafer in a flippedconfiguration, e.g., as shown in FIG. 12E, and then printed in a normalconfiguration with first and second stamps 30, 40, as described above byflipping components 20 a second time, or directly in a flippedconfiguration from the handle substrate with only one first stamp 30.

Substrate 10 can be a source wafer 10 (e.g., a component source wafer 10or native component source wafer 10) and each component 20 can bedisposed completely and entirely over a sacrificial portion 14. Incertain embodiments, source wafer 10 (substrate 10) can be any structurewith a surface suitable for forming patterned sacrificial layers 12,sacrificial portions 14 (or etched gap 15), anchors 16, tethers 18, anddisposing or forming patterned components 20. For example, source wafers10 can comprise a semiconductor or compound semiconductor and cancomprise an etchable sacrificial layer 12 comprising material different(e.g., an oxide) from material of source wafer 10. Any one or more ofsource wafer 10, sacrificial layer 12, and sacrificial portion 14 cancomprise an anisotropically etchable material. Suitable semiconductormaterials can be silicon or silicon with a (100) crystal structure(e.g., orientation). A surface of source wafer 10 can be substantiallyplanar and suitable for photolithographic processing, for example asfound in the integrated circuit or MEMs art.

In some embodiments of the present disclosure, components 20 are smallintegrated circuits or micro-electro-mechanical (MEMS) devices, forexample chiplets (e.g., micro-chiplets). Component 20 can have anysuitable aspect ratio or size in any dimension and any useful shape, forexample a rectangular cross section or rectangular top or rectangularbottom surface. Components 20 can be micro-components, for examplehaving at least one dimension that is in the micron range, for examplehaving a planar extent from 2 microns by 5 microns to 200 microns by 500microns (e.g., an extent of 2 microns by 5 microns, 20 microns by 50microns, or 200 microns by 500 microns) and, optionally, a thickness offrom 200 nm to 200 microns (e.g., at least or no more than 2 microns, 20microns, or 200 microns). Components 20 can have a thin substrate withat least one of (i) a thickness of only a few microns, for example lessthan or equal to 25 microns, less than or equal to 15 microns, or lessthan or equal to 10 microns, (ii) a width of 5-1000 microns (e.g., 5-10microns, 10-50 microns, 50-100 microns, or 100-1000 microns) and (iii) alength of 5-1000 microns (e.g., 5-10 microns, 10-50 microns, 50-100microns, or 100-1000 microns).

Such micro-components 20 can be made in a native source semiconductorwafer (e.g., a silicon wafer) having a process side and a back side usedto handle and transport the wafer using lithographic processes.Components 20 can be formed using lithographic processes in an activelayer on or in the process side of source wafer 10. Methods of formingsuch structures are described, for example, in U.S. Pat. No. 8,889,485.According to some embodiments of the present disclosure, source wafers10 can be provided with components 20, sacrificial layer 12 (a releaselayer), sacrificial portions 14, and tethers 18 already formed, or theycan be constructed as part of a process in accordance with certainembodiments of the present disclosure.

In certain embodiments, components 20 can be constructed using foundryfabrication processes used in the art. Layers of materials can be used,including materials such as metals, oxides, nitrides and other materialsused in the integrated-circuit art. Components 20 can have differentsizes, for example, less than 1000 square microns or less than 10,000square microns, less than 100,000 square microns, or less than 1 squaremm, or larger. Components 20 can have, for example, at least one of alength, a width, and a thickness of no more than 500 microns (e.g., nomore than 250 microns, no more than 100 microns, no more than 50microns, no more than 25 microns, or no more than 10 microns).Components 20 can have variable aspect ratios, for example at least 1:1,at least 2:1, at least 5:1, or at least 10:1. Components 20 can berectangular or can have other shapes.

A component 20 can be an active circuit component, for example includingone or more active electronic components such as electronic transistorsor diodes or light-emitting diodes or photodiodes that produce anelectrical current in response to ambient light. A component 20 can be apassive component, for example including one or more passive elementssuch as resistors, capacitors, or conductors. In some embodiments, acomponent 20 includes both active and passive elements. A component 20can be a semiconductor device having one or more semiconductor layers,such as an integrated circuit. A component 20 can be an unpackaged die.In some embodiments, a component 20 is a compound device 20 having aplurality of active or passive elements, such as multiple semiconductorcomponents with separate substrates, each with one or more activeelements or passive elements, or both. Components 20 can be or include,for example, electronic processors, controllers, drivers, light-emittingdiodes, photodiodes, light-control devices, light-management devices,piezoelectric devices, acoustic wave devices (e.g., acoustic wavefilters), optoelectronic devices, electromechanical devices (e.g.,microelectromechanical devices), photovoltaic devices, sensor devices,photonic devices, magnetic devices (e.g., memory devices), or elementsthereof.

As is understood by those skilled in the art, the terms “over” and“under” are relative terms and can be interchanged in reference todifferent orientations of the layers, elements, and substrates includedin the present disclosure. For example, a first layer on a second layer,in some implementations means a first layer directly on and in contactwith a second layer. In other implementations, a first layer on a secondlayer includes a first layer and a second layer with another layertherebetween.

Having described certain implementations of embodiments, it will nowbecome apparent to one of skill in the art that other implementationsincorporating the concepts of the disclosure may be used. Therefore, thedisclosure should not be limited to certain implementations, but rathershould be limited only by the spirit and scope of the following claims.

Throughout the description, where apparatus and systems are described ashaving, including, or comprising specific components, or where processesand methods are described as having, including, or comprising specificsteps, it is contemplated that, additionally, there are apparatus, andsystems of the disclosed technology that consist essentially of, orconsist of, the recited components, and that there are processes andmethods according to the disclosed technology that consist essentiallyof, or consist of, the recited processing steps.

It should be understood that the order of steps or order for performingcertain action is immaterial so long as the disclosed technology remainsoperable. Moreover, two or more steps or actions in some circumstancescan be conducted simultaneously. The disclosure has been described indetail with particular reference to certain embodiments thereof, but itwill be understood that variations and modifications can be effectedwithin the spirit and scope of the claimed invention.

PARTS LIST

-   -   10 substrate/source wafer    -   12 sacrificial layer    -   14 sacrificial portion/sacrificial material    -   15 gap    -   16 anchor    -   18 tether    -   20 component    -   21 first side    -   22 second side    -   24 encapsulation layer    -   26 component structure    -   28 component edge/component side    -   30 stamp/first stamp    -   32 rigid support    -   34 bulk layer    -   36 post/first post    -   38 common layer    -   39 pedestal    -   40 second stamp    -   46 second post    -   50 target substrate    -   60 motion platform    -   99 micro-transfer structure    -   100 provide source wafer with components step    -   110 provide first stamp step    -   120 contact component first side with first stamp step    -   130 remove first stamp from source wafer step    -   140 provide second stamp step    -   150 contact component second side with second stamp step    -   160 remove first stamp from component and second stamp step    -   170 provide target substrate step    -   180 contact component first side to target substrate step    -   190 remove second stamp from components and target substrate        step

The invention claimed is:
 1. A micro-transfer structure, comprising: afirst stamp comprising a rigid support, an elastomeric bulk layerdisposed on the rigid support, and first elastomeric posts disposed onthe bulk layer; and components each having a first side and an opposingsecond side, wherein the components are adhered to some but not all ofthe first posts on the first sides of the component, wherein each of thecomponents is adhered to two or more of the first posts; and a secondstamp different from the first stamp, the second stamp comprising asecond rigid support, a second elastomeric bulk layer disposed on thesecond rigid support, and second posts disposed on the secondelastomeric bulk layer, wherein the second sides of the components areadhered to the second stamp, and wherein each component of thecomponents is adhered to fewer second posts of the second stamp thanfirst posts of the first stamp.
 2. The micro-transfer structure of claim1, wherein only one second post is adhered to each of the components. 3.The micro-transfer structure of claim 2, wherein not all of the secondposts are adhered to the components.
 4. The micro-transfer structure ofclaim 1, wherein each first post of the first posts has a distal endwith a first post area, each second post of the second posts has adistal end with a second post area, and the second post area of each ofthe second posts is greater than the first post area of each of thefirst posts.
 5. The micro-transfer structure of claim 4, wherein, foreach of the components, the sum of the first post areas of the firstposts in contact with the component is smaller than the sum of thesecond post areas of the second posts in contact with the component. 6.The micro-transfer structure of claim 1, comprising a motion platformand the first rigid support is in contact with and controlled by themotion platform and the second rigid support is in contact with andcontrolled by the motion platform.
 7. The micro-transfer structure ofclaim 1, wherein the second posts have a greater adhesion to thecomponents than the first posts.
 8. A method of making a micro-transferprinted structure, comprising: providing a source wafer with componentsdisposed in, on, or over the source wafer; providing a stamp comprisinga rigid support, an elastomeric bulk layer disposed on the rigidsupport, and posts disposed on the bulk layer, wherein the rigid supportis less flexible than the bulk layer; contacting the stamp to thecomponents without first aligning the stamp to the source wafer suchthat some but not all of the posts adhere to the components and two ormore of the posts adhere to each of the components; and removing thecomponents from the source substrate by separating the stamp from thesource wafer such that the components remain adhered to the stamp.
 9. Amethod of making a micro-transfer printed structure, comprising:providing a source wafer with components disposed in, on, or over thesource wafer; providing a first stamp comprising a rigid support, anelastomeric bulk layer disposed on the rigid support, and first postsdisposed on the bulk layer; contacting the first posts to the componentsthereby adhering the first posts to the components, wherein two or moreof the first posts are adhered to each of the components; and removingthe first stamp with the components adhered from the source substrate,providing a second stamp different from the first stamp, the secondstamp comprising a second rigid support, a second elastomeric bulk layerdisposed on the second rigid support, and second posts disposed on thesecond bulk layer, and contacting the second posts to the components ona side of the components opposite the first posts thereby adhering thecomponents to the second stamp while the components are adhered to thefirst stamp, wherein, for each of the components, fewer of the secondposts are adhered to the component than first posts are adhered to thecomponent and the area of the second posts adhered to the component isgreater than the area of the first posts adhered to the component. 10.The method of claim 9, comprising removing the first stamp, contactingthe components to a target substrate with the second stamp, and removingthe second stamp from the components, thereby disposing the componentson the target substrate.
 11. A micro-transfer structure, comprising: astamp comprising a rigid support and posts disposed on or over the rigidsupport; and components adhered to some but not all of the posts, andwherein each of the components is adhered to two or more of the posts,at least some of the posts are not in contact with any component, and atleast one pair of adjacent ones of the components are separated by adistance that is smaller than a length, a width, or both a length and awidth of either of the adjacent ones of the components with at least oneof the posts on which no component is adhered disposed therebetween. 12.The micro-transfer structure of claim 11, wherein relative orientationor position of the components with respect to the posts is different fordifferent components.
 13. The micro-transfer structure of claim 11,wherein each post has (i) a substantially planar distal end, (ii) acontiguous distal end, or (iii) both (i) and (ii).
 14. Themicro-transfer structure of claim 11, comprising a source substrate,wherein the components are disposed on the source substrate.
 15. Themicro-transfer structure of claim 11, comprising a target substrate,wherein the components are disposed on the target substrate.
 16. Themicro-transfer structure of claim 11, comprising a motion platform,wherein the rigid support is in contact with and controlled by themotion platform.
 17. The micro-transfer structure of claim 11, whereineach of the components is adhered to at least six of the posts.
 18. Themicro-transfer structure of claim 11, wherein the posts are arranged inrows and columns, each of the components has an edge, and the edge isaligned with a row of the rows or a column of the columns.
 19. Themicro-transfer structure of claim 11, wherein each post of the posts hasa distal end with a post area, each component has a component area, andthe post area is less than one half of the component area.
 20. Themicro-transfer structure of claim 11, wherein each of the posts has acontact surface disposed in a common plane.
 21. The micro-transferstructure of claim 11, wherein the posts are not aligned to thecomponents.
 22. The micro-transfer structure of claim 14, wherein thestamp is not aligned to the source substrate.
 23. The method of claim 8,wherein relative orientation or position of the components with respectto the posts is different for different components.
 24. The method ofclaim 8, comprising printing the component from the stamp to a targetsubstrate by contacting the components to the target substrate with thestamp and separating the stamp from the components while the componentsremain disposed on the target substrate.
 25. The method of claim 9,wherein (i) some but not all of the first posts are adhered to thecomponents and two or more of the first posts are adhered to each of thecomponents while the components are adhered to the first stamp and (ii)some but not all of the second posts are adhered to the components andtwo or more of the second posts are adhered to each of the componentswhile the components are adhered to the second stamp.
 26. The structureof claim 11, wherein each pair of adjacent ones of the components hasones of the posts to which no component is adhered distributedtherebetween.
 27. The structure of claim 11, wherein the posts aredisposed in a regular array and ones of the posts to which no componentis adhered are distributed throughout the regular array between adjacentones of the components.
 28. The structure of claim 11, wherein relativeorientation or position of the components with respect to the posts isdifferent for different components.
 29. The structure of claim 11,wherein the length, the width, or both the length and the width is nomore than 1000 microns.
 30. The structure of claim 11, wherein thelength, the width, or both the length and the width is no more than 250microns.
 31. The structure of claim 1, wherein more than one of thesecond posts is adhered to each of the components.
 32. The structure ofclaim 31, wherein not all of the second posts are adhered to thecomponents.
 33. The micro-transfer structure of claim 11, wherein thestamp comprises an elastomeric bulk layer disposed on the rigid support,the posts are elastomeric posts disposed on the bulk layer, and therigid support is less flexible than the bulk layer.
 34. Themicro-transfer structure of claim 33, wherein the bulk layer comprises asingle contiguous common layer disposed on the rigid support and one ormore pedestals disposed on the common layer on a side of the commonlayer opposite the rigid support, wherein two or more posts are disposedon each of the one or more pedestals.
 35. The micro-transfer structureof claim 34, wherein the pedestals are at least as flexible as thecommon layer.
 36. The micro-transfer structure of claim 33, wherein thebulk layer and the posts are more flexible than the rigid support. 37.The micro-transfer structure of claim 33, wherein the elastomeric bulklayer is a single, contiguous layer, the stamp comprises no other bulklayer than the elastomeric bulk layer, and the posts are disposeddirectly on and in contact with the elastomeric bulk layer.
 38. Themicro-transfer structure of claim 33, wherein the posts aresubstantially identical and are disposed in a regular array on the bulklayer.